Method and Apparatus For Limiting Peer-to-Peer Communication Interference

ABSTRACT

Peer-to-peer communication between user terminals in a licensed spectrum is enabled by a method comprising the following steps: —communicating directly, peer-to-peer, between the first and the second mobile terminal, and —disconnecting the peer-to-peer communication in dependence of control signals received or not received from the base station. Thus, according to the invention, the network is enabled to control the peer-to-peer communication between two user terminals.

TECHNICAL FIELD

The present invention relates to a mobile terminal as defined in thepreamble of claim 1 and a base station as defined in the preamble ofclaim 8. The invention also relates to a method of communication betweena first and a second mobile terminal in a wireless network as defined inthe preamble of claim 13.

BACKGROUND AND PRIOR ART

Radio spectrum is a limited resource in wireless networks. Therefore,intense efforts are made to use the available spectrum as efficiently aspossible. With increasing demands for data communication and high bitrates this will become even more important in the future.

Typically different parts of the radio spectrum are licensed out tooperators who build communications systems utilizing the relevant parts.These systems may be seen as the primary systems in each respective partof the radio spectrum.

When a piece of licensed radio spectrum is not used for a period of timefor its primary purpose in a certain geographical network, for example,for wide area cellular communication, there will be a desire to use itfor other purposes.

A potentially important use could be short range peer-to-peercommunication, that is, direct communication without the use ofintermediary nodes such as base stations, between the user terminalsused in the primary communication system of the licensed spectrum.

A typical use of peer-to-peer communication could be over shortdistances, for example, for communication between one person's cellphoneand laptop, or between two laptops on the same desk. Short distancemeans that a rather low transmit power is sufficient and hence that asingle radio resource (frequency, time slot) that is not used for theprimary system can be re-used for many simultaneous peer-to-peercommunication sessions in physically separated places. Hence, a highertotal throughput can be obtained within the given spectrum, compared tocommunicating through the primary system. This type of peer-to-peercommunication can also be seen as a natural part of an “always bestconnected” concept, that is, to ensure that the type of connectionutilizing the network resources in the most efficient way at any giventime is always selected.

However, since peer-to-peer communication would take place in a licensedspectrum, network operators may be expected to require control of radioresources and the interference in the network. Prior art solutions forpeer-to-peer communication do not account for this need.

The TETRA (Terrestrial Trunked Radio) concept provides a Managed DirectMode (MDMO), described in the ETSI standard EN300396-10: “Managed DirectMode Operation (M-DMO) enables the use of DMO to be controlled byproviding a mechanism by which frequencies may be given for DMO use fora period of time. The objective of M-DMO is to constrain thetransmission by the M-DMO terminals such that they will not transmit ina geographical area in which they are not authorized to transmit”. Thedirect transmission between terminals is restricted by a broadcastsignal indicating which mobile terminals are allowed to use the directmode. There are no restrictions based on the actual effect of thepeer-to-peer communication on the network.

OBJECT OF THE INVENTION

It is an object of the invention to enable direct communication betweenterminals in a wireless network while maintaining operator control ofcommunication quality in the network.

SUMMARY OF THE INVENTION

This object is achieved according to the present invention by a mobileterminal for use in a wireless communication network said terminalcomprising means for communicating with a base station in saidcommunication network, said mobile terminal being characterized in thatit comprises

-   -   communication means for initiating direct communication directly        with said other mobile terminal,    -   control means for disconnecting said direct communication in        dependence of signals received or not received from the base        station.

The object is also achieved by a base station for use in a wirelesscommunication network, said base station comprising communication meansfor communicating with at least one mobile terminal in the mobilecommunication network, said base station further comprising

control means for controlling peer-to-peer communication between atleast a first and a second mobile terminal in the network bytransmitting to at least one of the terminals at least one signalindicating whether or not the mobile terminal may engage in peer-to-peercommunication.

The object is further achieved by a method of establishing communicationbetween a first and at least a second mobile terminal in a wirelesscommunication network, said method comprising the following steps:

-   -   communicating directly, peer-to-peer, between the first and the        second mobile terminal.    -   disconnecting the peer-to-peer communication in dependence of        control signals received or not received from the base station.

According to the invention, peer-to-peer communication is allowed, butmay be controlled by the network, by means of control signalstransmitted from the base station to one of the terminals participatingin the communication, or to both, or all, terminals.

The apparatuses and method according to the invention enables centralcontrol and supervision of peer-to-peer communication. Thereby,peer-to-peer communication in a licensed spectrum is enabled without thedrawbacks mentioned above. The peer-to-peer communication may be allowedor denied, for example, in dependence of the traffic situation in thenetwork.

The peer-to-peer communication can be arranged with minor or no changesto the hardware of the terminals and base stations, since the radiointerface is already pre-sent in the terminals. Also, it becomespossible for the network operator to charge for the use of theoperator's spectrum.

The communication means is preferably arranged to probe the power levelin direct, peer-to-peer, communication with another mobile terminal.This may, for example, be done by gradually increasing the power levelduring probing. Such probing will result in the lowest possible powerlevel, and therefore a minimum level of generated interference.Alternatively, a maximum allowed power level may be defined, as themaximum power level where no complaints are received from any basestation or other terminal. Probing may also be carried out bytransmitting at a fix power level. This enables immediate peer-to-peercommunication between the terminals.

The communication means may be arranged to apply a peer-to-peeridentifier to the communication. The peer-to-peer identifier may be asingle bit indicating that the communication is peer-to-peercommunication, or a unique identifier for the peer-to-peer communicationsession. The peer-to-peer identifier may also be implicit in thecommunication, such as a predefined pattern of power level variationsused for ramping and/or during the communication session.

To implement this function, the mobile terminal may also compriseinterference means for identifying interference from peer-to-peercommunication in the wireless communication network and for reportingsaid interference to the base station. This will enable decisions onwhether or not peer-to-peer communication should be allowed, based onhow such communication actually influences the network. Of course, thisfunction may also be implemented in telephones that do not themselveshave the functions required for peer-to-peer communication according tothe invention.

In this way the actual effect of the peer-to-peer communication on othercommunication in the network can be taken into account and peer-to-peercommunication which disturbs other communication can be terminated orallowed to continue with lower power levels.

The peer-to-peer identifier may be assigned to the respective terminalor communication session by the network, or it may be selected by peers.

The control means of the base station may be arranged to send said atleast one signal in response to a request received from the firstterminal. The control means may also be arranged to send said at leastone signal in response to disturbance information received from otherterminals.

For example, the control means may be arranged to send a signal ifpeer-to-peer communication is allowed and/or if peer-to-peercommunication is not allowed.

In one embodiment, the control means of the base station is arranged todetermine if peer-to-peer communication is allowed on the basis ofinterference information received from at least a third mobile terminalin the network.

The inventive method may be initiated by the first mobile terminalsignalling to a base station in the wireless network to requestpermission to communicate directly with the second mobile terminalbefore starting peer-to-peer communication.

By allowing peer-to-peer traffic in the licensed spectrum networkoperators may offer new services and, at the same time, increase thetraffic volume in the network. With network controlled peer-to-peertraffic the spectrum utilization can be increased. It may sometimes bedesirable to allow peer-to-per admission even if it would prevent orinterfere with normal traffic in the network, since the alternative maybe to use the radio resources of the network. According to the inventionthe network can control the traffic according to information only foundin the network about the use of network resources.

Peer-to-peer communication is mainly interesting for communication atshort distances and high bit rates. Transmission latency may besignificantly reduced if network nodes are not involved. For end usersthe peer-to-peer transmissions in the licensed spectrum may be morereliable than in the unlicensed spectrum, in particular when, asaccording to the invention, the use is under network control andsupervision.

Two or more terminals may engage in peer-to-peer communication.Broadcast is possible, in which one terminal transmits the same signalto a number of other terminals. Alternatively, two or more terminals maycommunicate as they find suitable.

A short transmission time interval (TTI) is advantageous, to ensure thatthe terminals check at relatively short intervals whether or notpeer-to-peer communication is still acceptable.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the following, by wayof example and with reference to the appended drawings in which:

FIG. 1 illustrates a mobile communication system in which the method maybe used.

FIG. 2 is a message sequence chart according to one embodiment of theinvention;

FIG. 3 is a flow chart according to a first embodiment of the invention;

FIG. 4 is a flow chart according to a second embodiment of theinvention;

FIG. 5 is a flow chart according to a third embodiment of the invention;

FIG. 6 illustrates, schematically, a mobile terminal comprising thefunctions needed according to the invention.

FIG. 7 is a flow chart of the method as experienced by the base station.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 illustrates a cellular network in which the invention can beimplemented. The network includes a number of base stations 1, eacharranged to communicate with one or more mobile terminals 3 within anarea often referred to as a cell. Usually, all communication betweenmobile terminals 3 passes through the network, that is, at least througha base station 1. If the mobile terminals 3 are located in differentcells, switching units and other units of the network, not shown in FIG.1, are also involved in ways well known in the art.

According to the invention, in certain circumstances, two mobileterminals can communicate directly with each other as indicated inFIG. 1. The basic function for enabling such direct communication, whichis often called peer-to-peer communication, according to the inventionis an admission control performed by a unit in the network, preferablythe base station. For these control functions, the base stationcomprises a control unit 11, in addition to the conventional units of abase station. Embodiments of the invention include probing and/oridentification of the communication, as will be discussed in more detailbelow.

The terminal initiating the peer-to-peer communication may be referredto as the “master” terminal and the other terminal may be referred to asthe “slave” terminal.

Probing. This is used to determine a suitable power level to use whencommunicating between the mobile terminals. Probing may be allowed onrequest from the terminal to the base station. Alternatively, probingmay alvays be allowed, or allowed according to a broadcast message.

Probing may be performed selectively on carriers/sub-carriers whereother signals are not detected, or on carriers/sub-carriers for whichthe network will allow it. It may be made necessary to carry out probingat regular time intervals, or after certain events in the network, toensure that minimum power levels are always used.

Probing may be performed by starting transmissions immediately at a fixpower level, which is known normally to be sufficient for short-rangecommunication. A more sophisticated way is to start with a lower powerlevel and successively increase the power until a sufficient level hasbeen reached. This principle is referred to as power ramping. This willresult in a minimum power level, and therefore a minimum level ofgenerated interference. The power during ramping may be any monotonousor non-monotonous function of time. During the probing phaseacknowledgement signals from the receiving terminal are used by theinitiating terminal to determine if the signal has been received, thatis, if the power level is sufficient.

During the probing phase mobile terminals that experience interferencefrom the peer-to-peer communication may report this to their servicebase station or the base station serving the mobile terminals engaged inpeer-to-peer communication. If the probing has not resulted inunacceptable interference levels, the serving base station admits thepeer-to-peer communication. Mobile terminals may report experiencedinterference during the peer-to-peer session as well. The base station'sreaction may be a P2P remove message to discontinue the peer-to-peersession or a P2P reduce message to reduce the power levels used for thepeer-to-peer session. Different power levels may be used by thedifferent terminals involved, for example, if one terminal is close to,and may disturb, other terminals, while the other terminal is locatedfurther away from other terminals.

Identification. Direct, or peer-to-peer traffic is identified so that itcan be recognized by other nodes or units in the network as such. Aspecific identifier is assigned to peer-to-peer communication to make itseparable from regular communication. Because of this, other nodes canlisten and object if their communication is interfered with. The use ofa specific identifier for peer-to-peer traffic ensures that terminalsthat are disturbed by regular, (not peer-to-peer) traffic report this tothe network.

Identification may be implicit in that a special pattern of rampingcharacteristics may be used to identify peer-to-peer transmissionindirectly through similar variations in CQI reports from interferedterminals.

Peer-to-peer identity may be only a single information bit (indicatingpeer-to-peer communication or not), or include a unique identity for thepeer-to-peer connection.

An identity number for each peer-to-peer connection may be assigned bythe network, or may be randomly selected by peers. The latter isparticularly useful if probing is to be performed without prior request.

Admission control. Peer-to-peer communication is only allowed when theinterference in the network can be kept at an acceptable level, so thatthe service quality is satisfactory. The admission control may beexecuted by the base station sending ok messages when the mobileterminal is allowed to transmit directly to another mobile terminal.Alternatively, the base station may send a not ok message when directcommunication is not allowed. In this case the terminal can continue totransmit if no explicit not ok message is received. Of course, the basestation may also send messages both when direct communication is allowedand when it is not.

A general broadcast message from the base station may be used toindicate if probing is allowed or not at a certain time. For example, ifthere is much traffic in the network peer-to-peer communication may notbe allowed at all and therefore no probing is permitted. At times whenthe traffic is low terminals may always be allowed to start probingwithout any request to the base station.

Admission control at the start of probing or communication is usuallyinitiated by the first mobile terminal requesting permission forprobing, or for starting peer-to-peer communication, from the basestation. It may also be executed during peer-to-peer communication. Forexample, if the base station receives reports from other mobileterminals that the peer-to-peer communication causes interference, itmay order the peer-to-peer communication to be terminated, or that thepower level be reduced. Alternatively, for continued communication to beallowed ok signals at regular intervals from the base station to one ormore of the terminals may be required. The signal may be sent to eitherof the terminals, or to both.

Admission may be given for the whole carrier, or one or more parts ofthe carrier. The permission to transmit may be signalled to one or bothpeers.

It may be possible that only one of the terminals is allowed totransmit, for example if the other terminal cannot transmit withoutdisturbing other traffic. In this case, the other terminal may beallowed to send acknowledge (ACK) and/or not acknowledge (NACK) signalsthrough the network instead of sending them peer-to-peer.

If admission is denied, the message may be accompanied by a suggestionfor another radio resource that may be probed, for example, anothercarrier.

If, at some point during peer-to-peer communication, it is determinedthat it disturbs other terminals in the network, the base station mayorder the peer-to-peer communication to end. Typically, before engagingin peer-to-peer conuniication again the terminal must wait a certainperiod of time and/or perform probing again.

It is possible that only a part of the traffic in the network isdisturbed, for example, only downlink or only uplink traffic. It islikely that downlink traffic may be more prone to disturbances.Therefore, it may be ordered that the terminals may use only thetime/frequency slots used for uplink for peer-to-peer communication. Ofcourse, they may also be allowed to use only the time/frequency slotsused for downlink in a similar way if this is found to be advantageous.In many cases, the terminal may know, or may be able to determine foritself, which time/frequency slots are used for uplink and downlink,respectively. If not, this information may be found in the ok messagetransmitted from the base station. The ok message may also compriseother types of limitations, for example, a maximum duration for thepeer-to-peer connection.

Charging for the communication may be made dependent on whether themaster or the slave, or both, or neither, are subscribers in the primarynetwork. Charging may also be based on how many other users areinterfered, how many are close enough to be potentially interfered, thepower used in the peer-to-peer communication, or other factors. Forexample, a lower rate may be used, or peer-to-peer communication may befree of charge, if the master terminal or both terminals are subscribersin the primary network. As another example, the peer-to-peercommunication may be free of charge if no other users are interfered.

FIG. 2 is a message sequence chart illustrating the signalling betweendifferent units in the network according to one embodiment of theinvention. The participating units are:

The first user terminal involved in the peer-to-peer communication, T1,the second user terminal involved in the peer to peer communication, T2,a third user terminal T3, which is not involved in the peer-to-peercommunication, T3, the first base station BS1, to which the first userterminal T1 is connected and the second base station BS2, to which thesecond user terminal T2 is connected. Of course, T1 and T2 may beconnected to the same base station, for example, to BS1.

According to this embodiment the signalling starts with the first userterminal T1 sending a probing request A to the first base station BS1.The base station responds by sending a probing ok message B. The firstterminal T1 then probes the second terminal T2 as discussed above. Theprobing signals are illustrated as two dashed lines C. The thirdterminal T3 listens to the probing signals between the first and thesecond terminal T1, T2. If the third terminal T3 experiencesinterference, or interference above a certain level, it may informeither the first base station BS1, or the base station to which it isconnected about this. The first base station then decides whether or notpeer-to-peer communication between the first and the second terminalshould be allowed, on the basis of any reports of interference from thethird, or any other, terminal. If no interference, or only interferencebelow a certain level, is reported, then an ok signal D will betransmitted from the base station BS1 to the mobile terminal T1, toindicate that peer-to-peer communication may proceed. The peer-to-peercommunication between the first and the second terminal T1, T2 isillustrated as three solid arrows E.

The third terminal T3 will continue to listen during the peer-to-peercommunication and may report interference at any time. As discussedabove, the peer-to-peer communication may be identified on the basis ofan identifier added to the messages, or a predefined power level patternduring probing. After a while new probing is performed, shown as dashedlines F, and a new ok signal G is received from the base station.Alternatively, the base station receives a disturbance indication fromthe third terminal T3 that it is being disturbed, shown as a dotted lineI, and sends a remove/reduce signal, also shown as a dotted line K tothe mobile terminal T1. After this remove/reduce signal thecommunication either continues with a lower power, or is terminated.

Both the message sequence chart in FIG. 2 and the flow charts in FIGS.3-5 below start at the point where a first terminal has decided that itwants to start peer-to-peer communication if possible. This point may bepreceded by other steps, such as a short sequence of signalling betweenthe first terminal and the terminal or terminals with which it wants tocommunicate. This is common in the art and is not discussed in anydetail here, since it is not important for the invention. Peer-to-peercommunication may also be initiated by the user of the terminal, or bythe base station. In the latter case, a command from the base station istransmitted to the terminal without any request from the terminal.

FIG. 3 is a flow chart of a first embodiment of the invention as seen bythe mobile terminal.

In step S31 the first, or master, terminal requests permission to startprobing for peer-to-peer communication with another terminal.

In step S32 the first terminal receives a “probing ok” signal from thebase station.

In step S33 the first and second terminals perform probing.

In step S34 a permission signal or a denial signal is received from thebase station in both the first and the second terminal, or just in thefirst terminal.

In step S35 the signal received from the base station is evaluated. Ifyes go to step S36; if no, end of procedure.

In step S36 peer-to-peer communication is performed between the firstand the second terminal.

In step S37 the terminal checks if a remove signal or a reduce signalhas been received from the base station. If a remove signal has beenreceived, go to step 39; if a reduce signal has been received, go tostep 38; if no signal has been received, return to step S36.

In step S38 the power level used by one or both terminals is reduced andthe procedure returns to step S36.

In step 39 the peer-to-peer communication is disconnected.

This method can be varied in a number of ways, for example, thefollowing.

Steps S31 and S32 may be omitted, for example if probing is alwaysallowed, or if a broadcast message has been distributed indicating thatprobing is allowed.

In step S33 the probing may be implicit, that is, it may be performedduring the peer-to-peer communication between the terminals.

In step S34 the permission, or the denial, may be implicit. In theformer case, peer-to-peer communication is allowed if no signal isreceived from the base station. In the latter case, peer-to-peercommunication is denied if no explicit ok signal is received from thebase station.

FIG. 4 is a flow chart of a second embodiment of the invention asexperienced by the terminal.

In step S41 the first, or master, terminal requests permission to startprobing for peer-to-peer communication with another terminal.

In step S42 the first terminal receives a “probing ok” signal from thebase station.

In step S43 the first and second terminal perform probing.

In step S44 a permission signal or a denial signal is received from thebase station in both the first and the second terminal, or just in thefirst terminal.

In step S45 the signal received from the base station is evaluated. Ifyes go to step S46; if no, end of procedure.

In step S46 peer-to-peer communication is performed between the firstand the second terminal.

In step S47 the terminal checks if an ok signal has been received fromthe base station. If an ok signal has been received, return to step S46;if no ok signal has been received, go to step S48.

In step 48 the peer-to-peer communication is disconnected.

As in FIG. 3, steps S41 and S42 may be omitted. In step S43 the probingmay be implicit. In step S44 the permission, or the denial, may beimplicit.

FIG. 5 is a flow chart of a simpler embodiment of the invention thanthose shown in FIGS. 3 and 4. In step S51 the mobile terminal simplystarts communicating with the second terminal. The communication maybegin with probing or may start right away. In step S52 an ok signal ora not ok signal is received from the base station. According to thisembodiment the terminal will continue to communicate until a not oksignal is received. The not ok signal may be a remove or reduce signal,that is, may order the terminals to disconnect, or to reduce the powerused for peer-to-peer communication. If a not ok signal is received thepeer-to-peer communication is disconnected in step S53. According to afirst variant of this embodiment, an ok signal from the base station isrequired after a certain period of time. In this case, the peer-to-peercommunication must be terminated if no ok signal is received from thebase station within a certain period of time after the beginning of thepeer-to-peer communication.

FIG. 6 illustrates a mobile terminal 3 according to the invention. Themobile terminal 3 comprises an antenna 31 for communicating with thebase station, and with other mobile terminals in peer-to-peercommunication. A transmit part 32 and a receive part 33 are connected tothe antenna. Both the transmit part 32 and the receive part 33 arecontrolled by a processor 34. All of this is well known in the art.According to the invention, in addition to the conventional functions ofthe terminal, the processor 34 comprises software functions forcontrolling the peer-to-peer communication, and the communication withthe base station related to the peer-to-peer communication.

In particular the processor 34 comprises a communication unit 35 forinitiating peer-to-peer communication with another mobile terminal and acontrol unit 36 for receiving signals from the base station related tothe peer-to-peer communication and to act upon these signals. Inparticular, the control unit 36 is arranged to receive and interpret okor not ok signals, or reduce signals, from the base station and start,continue, or disconnect the peer-to-peer communication as ordered bythese signals. The control unit 36 may also be arranged to transmit aprobe request to the base station and to wait for a response from thebase station before probing or transmitting. Thus, the control unit 36controls the peer-to-peer communication performed by the communicationunit 35.

According to an embodiment of the invention the communication unit 35 isarranged to transmit probing signals to the second mobile terminalbefore engaging in communication. The probing signals may be sent with afix power level which is assumed to be appropriate, or may start at alower power level and increase if necessary, as discussed above.

According to an embodiment of the invention the communication unit 35 isarranged to add an identifier to the peer-to-peer probes andpeer-to-peer communication, to enable the base station, and otherterminals that may be disturbed by it to identify it as peer-to-peer andreport this to the base station. Accordingly the processor alsocomprises interference means 37 arranged to detect any disturbingtraffic caused by other terminals and, if it is identified aspeer-to-peer communication based on said identifier, report thedisturbance to the base station.

As the skilled person will understand the different units 35, 36, 37 arelogical units only, intended for illustration purposes. Of course, thefunctions could be performed by the same unit, or be distributed ondifferent units as is found to be functional.

FIG. 7 is a flow chart of the method as experienced by the base station.Again, as will be obvious from the above discussions, a number ofvariants are possible.

In step S71 a request from a terminal to start probing for peer-to-peercommunication with another terminal is received.

In step S72 the base station determines if it is ok to start probing. Ifyes, go to step S73; if no, go to step 76.

In step S73 the base station sends a response to the mobile terminalindicating if probing is acceptable.

In step S74 the base station determines if any reports of interferencecaused by the peer-to-peer communication has been received. If yes; goto step S76, if no, go to step S75.

Step S75: the base station sends a response to the mobile terminalindicating that it is ok to start peer-to-peer communication and returnsto step S74.

Step S76: the base station indicates to the mobile terminal that probingand/or peer-to-peer communication is not allowed and, if ongoing, shouldbe terminated.

As before, steps S71 and S72 are optional and may be omitted. Theterminal may start probing and/or communicating without explicitlyrequesting permission from the base station. The signalling in stepsS73, S75 and S76 may in each case be replaced by implicit ok or not oksignals, respectively. In steps S73 and S75 this would mean that ifpeer-to-peer communication is allowed, no signal is sent from the basestation. The terminal can then engage in peer-to-peer communicationuntil a reduce/remove command is received from the base station.Conversely, in step S76 the command to stop peer-to-peer communicationmay be implicit in that an ok signal is required at certain times forthe terminal to continue peer-to-peer communication. In step S76 thebase station may also send a peer-to-peer reduce signal to the mobileterminal, to indicate that the peer-to-peer communication may continuebut with a reduced power level.

1. A mobile terminal for use in a wireless communication network said terminal comprising means for communicating with a base station in said communication network, said mobile terminal comprising communication means for initiating direct communication directly with another mobile terminal control means for disconnecting said direct communication in dependence of signals received or not received from the base station.
 2. A mobile terminal according to claim 1, in which the communication means is arranged to probe the power level in direct, peer-to-peer, communication with another mobile terminal.
 3. A mobile terminal according to claim 2, wherein the communication means is arranged to probe the power level by gradually increasing the power level during probing.
 4. A mobile terminal according to claim 1, wherein the communication means is arranged to apply a peer-to-peer identifier to the communication.
 5. A mobile terminal according to claim 4, wherein the peer-to-peer identifier is a single bit indicating that the communication is peer-to-peer communication.
 6. A mobile terminal according to claim 4, wherein the peer-to-peer identifier is a unique identifier for the peer-to-peer communication session.
 7. A mobile terminal according to claim 1 further comprising interference means for identifying interference from peer-to-peer communication in the wireless communication network and for reporting said interference to the base station.
 8. A base station for use in a wireless communication network, said base station comprising communication means for communicating with at least one mobile terminal in the mobile communication network, said base station further comprising Control means for controlling peer-to-peer communication between at least a first and a second mobile terminal in the network by transmitting to at least one of the terminals at least one signal indicating whether or not the mobile terminal may engage in peer-to-peer communication.
 9. A base station according to claim 8, wherein the control means is arranged to send said at least one signal in response to a request received from the first terminal.
 10. A base station according to claim 8, wherein the control means is arranged to send a signal if peer-to-peer communication is allowed.
 11. A base station according to, claim 8 wherein the control means is arranged to send a signal if peer-to-peer communication is not allowed.
 12. A base station according to, claim 8, wherein the control means is arranged to determine if peer-to-peer communication is allowed on the basis of interference information received from at least a third mobile terminal in the network.
 13. A method of establishing communication between a first and a second mobile terminal in a wireless communication network, said method comprising the following steps: communicating directly, peer-to-peer between the first and the second mobile terminal. disconnection the peer-to-peer communication in dependence of control signals received or not received from the base station.
 14. A method according to claim 13, further comprising the step of the first mobile terminal signalling to a base station in the wireless network to request permission to communicate directly with the second mobile terminal before starting peer-to-peer communication.
 15. A method according to claim 13, further comprising the step of probing between the first and second mobile terminal to determine a suitable power level.
 16. A method according to claim 15, wherein the probing is performed by means of power ramping.
 17. A method according to claim 13, further comprising the step of adding an identifier to the peer-to-peer communication to identify it as peer-to-peer communication.
 18. A method according to claim 13, further comprising the step of disconnecting the peer-to-peer communication if a remove signal is received from the base station.
 19. A method according to claim 13, further comprising the step of reducing the power used for peer-to-peer communication if a reduce signal is received from the base station.
 20. A method according to claim 13, further comprising the step of disconnecting the peer-to-peer communication if an ok signal is not received from the base station. 